netdev - Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta

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Message-ID: <CADVnQykJWYw=M8L=nXnkWN64a2=q6KRssmn3SK0hGFjT4V47zQ@mail.gmail.com>
Date: Mon, 23 Sep 2024 21:58:13 -0400
From: Neal Cardwell <ncardwell@...gle.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Paolo Abeni <pabeni@...hat.com>, Josh Hunt <johunt@...mai.com>, edumazet@...gle.com, 
	davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta_us()

On Mon, Sep 23, 2024 at 8:37 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> On Fri, Sep 20, 2024 at 1:36 AM Neal Cardwell <ncardwell@...gle.com> wrote:
> >
> > On Thu, Sep 19, 2024 at 5:05 AM Paolo Abeni <pabeni@...hat.com> wrote:
> > >
> > > On 9/10/24 21:08, Josh Hunt wrote:
> > > > diff --git a/include/net/tcp.h b/include/net/tcp.h
> > > > index 2aac11e7e1cc..196c148fce8a 100644
> > > > --- a/include/net/tcp.h
> > > > +++ b/include/net/tcp.h
> > > > @@ -2434,9 +2434,26 @@ static inline s64 tcp_rto_delta_us(const struct sock *sk)
> > > >   {
> > > >       const struct sk_buff *skb = tcp_rtx_queue_head(sk);
> > > >       u32 rto = inet_csk(sk)->icsk_rto;
> > > > -     u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto);
> > > >
> > > > -     return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
> > > > +     if (likely(skb)) {
> > > > +             u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto);
> > > > +
> > > > +             return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
> > > > +     } else {
> > > > +             WARN_ONCE(1,
> > > > +                     "rtx queue emtpy: "
> > > > +                     "out:%u sacked:%u lost:%u retrans:%u "
> > > > +                     "tlp_high_seq:%u sk_state:%u ca_state:%u "
> > > > +                     "advmss:%u mss_cache:%u pmtu:%u\n",
> > > > +                     tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
> > > > +                     tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
> > > > +                     tcp_sk(sk)->tlp_high_seq, sk->sk_state,
> > > > +                     inet_csk(sk)->icsk_ca_state,
> > > > +                     tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
> > > > +                     inet_csk(sk)->icsk_pmtu_cookie);
> > >
> > > As the underlying issue here share the same root cause as the one
> > > covered by the WARN_ONCE() in tcp_send_loss_probe(), I'm wondering if it
> > > would make sense do move the info dumping in a common helper, so that we
> > > get the verbose warning on either cases.
> >
> > That's a good idea. It would be nice to move the info dumping into a
> > common helper and use it from both tcp_rto_delta_us() and
> > tcp_send_loss_probe(), if Josh is open to that.
>
> Hello Paolo, Neal,
>
> I noticed that this patch got merged already. Since extracting the
> common part into a helper belongs to net-next materials, if no one is
> willing to do it after net-next is re-opened, I think I can post it :)

Thanks, Jason. That sounds fine to me. I don't have cycles to work on that.

Thanks,
neal